Coronary artery disease (CAD) is the leading cause of mortality and disability in the western world. Since the signal event of CAD is often sudden death or myocardial infarction, great energy has been focused on developing new noninvasive imaging technologies to identify patients at risk for CAD and/or its devastating consequences. Positron emission tomography (PET) with the new flow tracer 18F-BMS is one of the most promising methods for detecting and localizing CAD, quantifying myocardial blood flow, and characterizing wall motion abnormalities using gated imaging techniques that have emerged in recent years. Current approaches to rest/stress myocardial perfusion imaging with either PET or Single-Photon Emission Computed Tomography (SPECT) require separate imaging at rest and under pharmacologic- or exercise-induced cardiac stress. Such repeat imaging requires post-processing rest-stress image coregistration, is time-consuming, inefficient, onerous to the patient, and requires repeated transmission or CT scans needed for attenuation correction that increase radiation does to the patient. Under this R21 project, we propose a new protocol for 18F-BMS cardiac PET based on a dual-injection single-scan technique for rapid rest/stress imaging. In this approach only a single scan is performed to complete the rest/stress protocol. At the beginning patient is injected with tracer at rest, dynamic data is acquired, and then after about 5-10 minutes (optimal delay to be determined) patient is stressed with the pharmacologic agent and a second administration of tracer (at stress) is performed without interrupting the scanning. Following the second injection, data acquisition is continued for another 5-10 minutes (duration to be optimized). Separate rest and stress images and quantitative parameters of perfusion are calculated from the data using signal separation techniques based on new multi-state kinetic compartmental models. The proposed multi-state single-scan technique offers several advantages. It would substantially increase patient throughput and scanner utilization due to the short time needed for completing the rest/stress myocardial study protocol. The coregistration between images at rest and stress needed for estimation of coronary flow reserve (CFR) would be improved because patients are not moved between rest and stress studies. The new approach also comes with benefits to the patient in reduced radiation dose because only one x-ray CT scan is necessary. The proposed signal-separation algorithms are more powerful than the simple background subtraction technique currently being employed when separating rest and stress signals. Although in this work we concentrate on cardiac 18F-BMS, the techniques developed under this grant will also be directly applicable to cardiac imaging with other tracers. Multi-state cardiac PET imaging has great potential to improve cardiac patient care by providing a faster, safer, and more effective way of performing quantitative perfusion imaging with PET.